Design of a Broadband Shortened Horn Loaded with a Flat Wire-Medium Annular Lens

"In this contribution, we present the design of a flat wire-medium annular lens to be applied to the aperture of a shortened horn antenna in order to achieve gain performances similar to the ones of the corresponding optimum horn over a broad frequency range. The lens operation is based on the phase-compensation concept and the wire-medium is designed such that it behaves as an epsilon near-zero metamaterial at the frequencies of interest. The annular shape of the lens allows adjusting the phase-front of the field propagating along the short flare of the horn in order to achieve an uniform phase distribution at the horn aperture and maximizing, thus, the gain. As an example, we report the design of the proposed lens for a C-band conical horn. The length of the horn is half the length of the optimum horn, while the obtained gain performances are similar to the ones of the optimal horn over the entire mono-modal frequency band of operation of the feeding waveguide. This result may open the door to several interesting applications in satellite and radar systems."